Tuning fork frequency adjuster



g 1965 w. o. BENNETT ETAL 3,202,343

TUNING FORK FREQUENCY ADJUSTER Original Filed Jan. 19, 1961 ELccTaJ/wcDIP/vs C I NVENTORS Mum/ 0. 56/7/1577 MAL/47M M Marni? United StatesPatent 2 Claims. Cl. 310-25 This invention relates generally toelectronicallycontrolled timepieces which incorporateelectromagnetically-actuated tuning forks, and more particularly to atuning fork structure whose generating frequency may be readily andprecisely adjusted. This application is a division of our copendingapplication Serial No. 89,896, filed January 19, 1961, now abandoned.

In ordinary electric watches, make-and-break contacts are mechanicallyoperated by the swinging of the balance wheel. Each time these contactsclose, battery current flows in a coil or coils to electro-magneticallyimpulse the balance wheel. This mechanically operated makeand-breakcontact system is subject to wear and also to deterioration andcontamination of the delicate contact points which must open and closean electric circuit without fail 216,000 times a day. The slightestsparking will cause rapid deterioration of these contacts and earlyfailure of the watch.

The present invention does away with a balance wheel and escapement aswell as make-and-break contacts and makes use of a timekeeping tuningfork which is pulsed electromagnetically by means of a transistorcircuit. It constitutes an improvement over timepieces of the typedisclosed in the copending applications Serial No. 665,480, filed June13, 1957, entitled Electronically- Controlled Timepiece, now Patent No.2,971,323, issued February 14, 1961, and in Serial No. 584,709, filedMay 14,1956, entitled Electrical Timepiece, now Patent No. 2,960,817,issued November 22, 1960.

In said copending applications there are disclosed novel timepiecesincluding a self-suflicient timekeeping standard formed by a tuning forkhaving a predetermined natural frequency and a battery-energizedtransistorized drive circuit to sustain the vibratory motion of thefork. This motion is transferred to a rotary movement including theusual gear train and dial pointers by means of a pawl attached to onetine of the fork, the pawl advancing a ratchet wheel which drives thegear train.

While it is possible in an electronic timepiece of the above-describedtype, even when mass producing the device, to predetermine the operatingfrequency within narrow limits, it is still necessary to be able to makea final and precise adjustment of the timing frequency.

Accordingly, it is the main object of the invention to provide a tuningfork structure whose operating fre ,quency may be readily and preciselyadjusted. More specifically, it is an object of the invention to providea frequency regulator which may be clipped onto the transducers attachedto the tines of the fork.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is made to the following detaileddescription to be read in conjunction with the accompanying drawingswherein like components in the several figures are identified by likereference numerals.

In the drawings:

FIG. 1 is a schematic representation, in perspective, of the basiccomponents of an electronic timepiece in accordance with the invention.

FIG. 2 is a separate elevational view of the tuning fork structureshowing the clipped-on regulators.

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FIG. 3 is a separate plan view of the timing regulator.

FIG. 4 is a side view of the regulator attached to the cup of themagnetic element.

Referring now to the drawings and more particularly to FIG. 1, the majorcomponents of a timepiece in accordance with the invention are atimekeeping standard constituted by a tuning fork 10 and an electronicdrive circuit 11 therefor, a rotary movement of conventional designincluding a gear train 12 for turning the hands of the timepiece, and amotion transformer including an index wheel 13 operatively intercouplingthe fork 10 and the rotary movement 12 and acting to convert thevibratory action of the fork into rotary motion. The tuning fork has nopivots or bearings and its timekeeping action is therefore independentof the effects of friction.

All of the electrical components of the drive circuit are mounted on twounitized sub-assembly units or modules F and F attached to a disc-shapedmetallic pillar plate 14 which may be supported within a Watch casing ofstandard design or within any other type of housing, depending on theuse to which the timepiece is put. The electrical components areconstituted by a transistor. TR, a battery B, a bias circuit R-C, and acapacitor C.

Tuning fork 10 is provided with a pair of flexible tines 15 and 16interconnected by a relatively inflexible base 17, the base beingprovided with an upwardly extending stem 18 secured to the pillar plateby suitable screws 19 and 20. The central area of the pillar plate iscut out to permit unobstructed vibration of the tines.

The tuning fork is actuated by means of a first transducer T constitutedby a magnetic element 21 secured to the free end of tine 15, the elementcoacting with a drive coil 22, and a phase sensing coil 23. Drive coil22 is wound on an open ended tubular carrier 24 aflixed to asub-assembly mounting form F which is secured to pillar plate 14. Coils22 and 23 may be wound in juxtaposed relation on carrier 24 or the phasesensing coil 23 may be wound over drive coil 22.

A second transducer T is provided constituted by a magnetic element 25secured to the free end of tine 16 and coacting with a drive coil 26wound on a tubular carrier 27.

As is well known, the tines of a vibrating fork normally oscillatetoward and away from each other. That is, inward movement of one tinefrom its normal rest position is accompanied by a corresponding inwardmovement of the other tine and outward movement of one tine isaccompanied by a corresponding outward movement of the other tine.

Although it is possible to manufacture tuning forks with a very smallmargin of error, in large scale production techniques it is stillnecessary as a practical matter to effect a final factory adjustment.Also adjustments are required to take care of differences arising fromthe ersonal habits of a wearer. In the present instance, the frequencyof the fork is determined not by the fork per se but by the combinedmass of the tines and their associated magnetic elements and to effectmatching of the tines it is necessary that symmetry exist as between thecenters of gravity of the two oscillating masses with respect to theaxis of symmetry of the fork. Also with aging of the fork over a periodof years, a further slight adjustment may be necessary if one wishes tomaintain the accuracy of the timepiece within a few seconds a week.

For the purpose of effecting a fine adjustment in operating frequency ofeach tine, there are attached to the magnetic elements 21 and 25,identical regulator devices 31 and 32, respectively. As shown separatelyin FIGS. 3 and 4, regulator 31 is constituted by a flat metal clippreferably made of beryllium copper alloy and having a pair of springfingers 31a and 31b which clamp about a rivet 1c inserted centrally atthe end of the associated magnetic cup, the clip lying against the baseof the cup. The spring fingers project from a bridge 31d whose arcuateupper edge is serrated to define a series. of spaced teeth t t t etc. Bythe use of a simple tool adapted to engage the teeth, the clip may beturned in either direction relative to the axis of the rivet to effectan angular displacement of the teeth.

The regulator clip in combination with its associated magnetic elementconstitutes a mass which loads the tine to which they are attached. Thefrequency of a tuning fork is dependent upon the effective length of thetin-es. Moving the regulators upward, away from the base of the fork,will effectively lengthen the tine by moving its center of gravity. Thiswill cause a slower rate. Conversely, moving a regulator down, towardthebase of the fork, will cause a faster rate.

Each tooth 1 etc., constitutes a minute component of the total mass, andas the clip is rotated, the resultant displacement in the center ofgravity produces a fine change in the operating frequency. In practice,the clip may be designed so that an angular displacement of the clipcorresponding to one tooth or groove between causes a two second. perday variation in the operating rate of the timepiece. Corrections assmall as /2 second a day can be easily made by moving the regulator onequarter of a division. Because of the basic accuracy of a tuning fork,corrections greater than a few seconds per day are not required. Infact, the total range in the regulator system shown is only 28 secondsper day.

While there has been shown what is considered to be a preferredembodiment of the invention, it will be obvious that many changes may bemade therein without departing from the essential spirit of theinvention as defined in the annexed claims.

What is claimed is:

1. An electromagnetically-actuated vibrator comprising a tuning forkhaving a pair of tines, and means for actuating said fork including atransducer constituted by a magnetic element attached to one of saidtines and formed by a cylindrical cup having a magnetic rod supportedcoaxially therein, a frequency regulator for said tine constituted by aspring clip having a pair of fingers clamping a rivet attached to thebase of said cup and pivotable thereon, said clip having a toothedbridge portion which when angularly displaced effectively shifts thecenter of gravity of said element.

2. A vibrator, as set forth in claim 1, wherein each of said tines isprovided with said element and said regulator thereon to eifect matchingof said tines as well as frequency control.

References Cited by the Examiner UNITED STATES PATENTS 3,070,951 1/63Hetzel 84-457 ORIS L. RADER, Primary Examiner.

MILTON O. HIRSHFIELD, Examiner.

1. AN ELECTROMAGNETICALLY-ACTUATED VIBRATORY COMPRISING A TUNING FORKHAVING A PAIR OF TINES, AND MEANS FOR ACTUATING SAID FORK INCLUDING ATRANSDUCER CONSTITUTED BY A MAGNETIC ELEMENT ATTACHED TO ONE OF SAIDTINES AND FORMED BY A CYLINDRICAL CUP HAVING A MAGNETIC ROD SUPPORTEDCOAXIALLY THEREIN, A FREQUENCY REGULATOR FOR SAID TINE CONSTITUTED BY ASPRING CLIP HAVING A PAIR OF FINGERS CLAMPING A RIVET ATTACHED TO THEBASE OF SAID CUP AND PIVOTABLE THEREON, SAID CLIP HAVING A TOOTHEDBRIDGE PORTION WHICH WHEN ANGULARLY DISPLACED EFFECTIVELY SHIFTS THECENTER OF GRAVITY OF SAID ELEMENT.